Pyruvate is reduced to lactate in anaerobic

metabolism in muscle cells

Transferases and hydrolases catalyze group

transfer reactions

Acyl transfer:

Hexokinase catalyzes a phosphoryl transfer

from ATP to glucose

Glycosidases are hydrolases, catalyzing

hydrolysis of glycosidic bonds

Lyases catalyze eliminations and the

formation/breaking of carbon-carbon bonds

Lyases catalyze eliminations and the

formation/breaking of carbon-carbon bonds

Isomerases catalyze isomerizations or

internal rearrangements

prolyl

isomerase

Ligases couple ATP (or NTP) hydrolysis with

bond formation

Enzymes can dramatically enhance reaction

rates

How do they do it?

Enzymes use several catalytic mechanisms

(often together) to enhance reaction rates

• Proximity and orientation effects: the enzyme specifically binds and

positions substrates (with respect to each other and to enzyme

functional groups) to maximize reactivity

• Electrostatic catalysis: the enzyme uses charge-charge interactions

in catalysis

• Preferential binding of transition state: binding interactions between

the enzyme and TS are maximized; they are greater than those in

the enzyme-substrate or enzyme-product complexes

• General acid and general base catalysis: functional groups of the

enzyme donate &/or accept protons

• Covalent catalysis: the enzyme forms a covalent bond with the

substrate

• Metal-ion catalysis: the enzyme uses a metal ion to aid catalysis

Enzymes bind their substrates with

geometric and electronic complementarity

Enzymes are stereoselective (ex: aconitase)

Binding complementarity positions

substrates to maximize reaction rates

Enzymes use several catalytic mechanisms

(often together) to enhance reaction rates

• Proximity and orientation effects: the enzyme specifically binds and

positions substrates (with respect to each other and to enzyme

functional groups) to maximize reactivity

• Electrostatic catalysis: the enzyme uses charge-charge interactions

in catalysis

• Preferential binding of transition state: binding interactions between

the enzyme and TS are maximized; they are greater than those in

the enzyme-substrate or enzyme-product complexes

• General acid and general base catalysis: functional groups of the

enzyme donate &/or accept protons

• Covalent catalysis: the enzyme forms a covalent bond with the

substrate

• Metal-ion catalysis: the enzyme uses a metal ion to aid catalysis

Enzymes use several catalytic mechanisms

(often together) to enhance reaction rates

• Proximity and orientation effects: the enzyme specifically binds and

positions substrates (with respect to each other and to enzyme

functional groups) to maximize reactivity

• Electrostatic catalysis: the enzyme uses charge-charge interactions

in catalysis

• Preferential binding of transition state: binding interactions between

the enzyme and TS are maximized; they are greater than those in

the enzyme-substrate or enzyme-product complexes

• General acid and general base catalysis: functional groups of the

enzyme donate &/or accept protons

• Covalent catalysis: the enzyme forms a covalent bond with the

substrate

• Metal-ion catalysis: the enzyme uses a metal ion to aid catalysis

Enzymes use several catalytic mechanisms

(often together) to enhance reaction rates

• Proximity and orientation effects: the enzyme specifically binds and

positions substrates (with respect to each other and to enzyme

functional groups) to maximize reactivity

• Electrostatic catalysis: the enzyme uses charge-charge interactions

in catalysis

• Preferential binding of transition state: binding interactions between

the enzyme and TS are maximized; they are greater than those in

the enzyme-substrate or enzyme-product complexes

• General acid and general base catalysis: functional groups of the

enzyme donate &/or accept protons

• Covalent catalysis: the enzyme forms a covalent bond with the

substrate

• Metal-ion catalysis: the enzyme uses a metal ion to aid catalysis

Acid-base and covalent catalysis rely on

nucleophile-electrophile chemistry

Enzymes use several catalytic mechanisms

(often together) to enhance reaction rates

• Proximity and orientation effects: the enzyme positions substrates

(with respect to each other and to enzyme functional groups) to

maximize reactivity

• Electrostatic catalysis: the enzyme uses charge-charge interactions

in catalysis

• Preferential binding of transition state: binding interactions between

the enzyme and TS are maximized; they are greater than those in

the enzyme-substrate or enzyme-product complexes

• General acid and general base catalysis: functional groups of the

enzyme donate &/or accept protons

• Covalent catalysis: the enzyme forms a covalent bond with the

substrate

• Metal-ion catalysis: the enzyme uses a metal ion to aid catalysis

Proteins use cofactors to expand their range

of functions

Carbonic anhydrase uses Zn2+ for catalysis

Enzymes use several catalytic mechanisms

(often together) to enhance reaction rates

• Proximity and orientation effects: the enzyme positions substrates

(with respect to each other and to enzyme functional groups) to

maximize reactivity

• Electrostatic catalysis: the enzyme uses charge-charge interactions

in catalysis

• Preferential binding of transition state: binding interactions between

the enzyme and TS are maximized; they are greater than those in

the enzyme-substrate or enzyme-product complexes

• General acid and general base catalysis: functional groups of the

enzyme donate &/or accept protons

• Covalent catalysis: the enzyme forms a covalent bond with the

substrate

• Metal-ion catalysis: the enzyme uses a metal ion to aid catalysis

Self test: Identify the enzyme class and

catalytic mechanisms used.

Self test: Identify the enzyme class and

catalytic mechanisms used.

Self test: Identify the enzyme class and

catalytic mechanisms used.

Self test: Identify the enzyme class and

catalytic mechanisms used.

Self test: Identify the enzyme class and

catalytic mechanisms used.